An air filter designed to remove particulate is generally a device composed of fibrous materials. These fibrous materials may remove solid particulates such as dust, pollen, mold, and bacteria from the air. Air filters are used in applications where air quality is important, notably in building ventilation systems and in engines.
Air filters may be used in automobiles, trucks, tractors, locomotives and other vehicles that use internal combustion engines. Air filters may be used with gasoline engines, diesel engines, or other engines that run on fossil fuels or other combustible substances. Air filters may be used with engines in which combustion is intermittent, such as four-stroke and two-stroke piston engines, as well as other types of engines that take in air so that a combustible substance may be burned. For example, air filters may be used with some gas turbines. Filters may also be used with air compressors or in other devices that take in air.
Filters may be made from pleated paper, foam, cotton, spun fiberglass, or other known filter materials. Generally the air intakes of internal combustion engines and compressors tend to use either: paper, foam, or cotton filters. Some filters use an oil bath. Air filters for internal combustion engines prevents abrasive particulate matter from entering the engine's cylinders, where it would cause mechanical wear and oil contamination. Many fuel injected engines utilize a flat panel pleated paper filter element. This filter is usually placed inside an enclosed, plastic box connected to a throttle body by way of ductwork. Vehicles that use carburetors or throttle body fuel injection systems typically use a cylindrical air filter positioned above the carburetor or the throttle body.
A drawback to enclosed air boxes that require flat panel paper filters is that as particulate matter builds up in the filter, air flow through the filter becomes restricted. Such a restricted air flow generally leads to a reduction in engine performance, such as a decrease in engine power output and a greater fuel consumption. Moreover, as the paper filter becomes increasingly clogged, pressure inside the filter decreases while the atmospheric air pressure outside the filter remains the same. When the difference in pressure becomes too great, contaminants may be drawn through the paper filter directly into the engine. Thus, the ability of the paper filter to protect the engine from contamination and internal damage tends to decrease near the end of the filter's service life. Typically, paper air filters are removed from the vehicle and discarded, and a new paper air filter is then installed. Considering that there are millions of vehicles throughout the world, the volume of discarded air filters that could be eliminated from landfills is a staggering number. Another drawback to enclosed air boxes is that they typically conduct air through a tortuous path of hoses or ductwork before the air enters the intake of the engine. In some cases, the air box is a greater source of air restriction than is the paper filter. Similar to a contaminated air filter, a restrictive air box decreases engine performance and fuel economy. What is needed, therefore, is an air intake system which exhibits reduced air resistance and includes an air filter which may be periodically cleaned and reused.